Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B25/00—Phosphorus; Compounds thereof
  • C01B25/16—Oxyacids of phosphorus; Salts thereof
  • C01B25/26—Phosphates
  • C01B25/38—Condensed phosphates
  • C01B25/40—Polyphosphates
  • C01B25/405—Polyphosphates of ammonium
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B25/00—Phosphorus; Compounds thereof
  • C01B25/16—Oxyacids of phosphorus; Salts thereof
  • C01B25/26—Phosphates
  • C01B25/28—Ammonium phosphates
• • C—CHEMISTRY; METALLURGY
  • C05—FERTILISERS; MANUFACTURE THEREOF
  • C05B—PHOSPHATIC FERTILISERS
  • C05B7/00—Fertilisers based essentially on alkali or ammonium orthophosphates

Definitions

• the object of the invention is a process for obtaining a totally water-soluble nitrogenous-phosphate fertilizer consisting essentially in using a wet process phosphoric acid; in removing the'fiuosili'cic acid from the said phosphoric acid in a known'manner' with a sodium salt, followed by separating out the insolubilized sodium fluosilicateyin ammoniating the defiuosilicated acid-to a'pH of 5 to 6, and preferably from 5.5 to 6; in removoing sub stantially all the water from the reaction mixture and in treating the resulting ammoniated phosphate in a' dry process with urea in amounts of from 0.2 to 0.9 molecule of urea per mole .of P 0 for to 70 minutes at a temperature of between 135 and 160 C., the mixture being subsequently left to cool and, if necessa y, diluted with water.
• This invention relates to fertilizers, and more particularly to a process for the manufacture of a nitrogenphosphate fertilizer wherein the available amount of phosphoric anhydride P 0 is totally water-soluble and is, therefore, suitable for the manufacture of liquid fertilizers.
• Liquid fertilizers have lately been used with increasing frequency, owing to the ease with which liquids can be handled and applied. These fertilizers are usually produced by ammoniating phosphoric acid produced by the thermal or wet process. Phosphate produced from phosphoric acid prepared by the thermal process is relatively pure and provides a clear solution, but for economical reasons phosphate obtained from phosphoric acid by the wet process is being used more andmore frequently. Unfortunately this product contains insolublecompounds such as iron, aluminum, calcium and magnesium phosphates which are troublesome in the liquid fertilizer industry which prefers solutions which are substantially free from solid precipitates.
• phosphoric acid is ammoniated to obtain a sufiiciently alkaline solution (ph 5) to make iron, aluminium, calcium and magnesium phosphates, as well as silica, insoluble under conditions ensuring the best possible filtering properties. Filtering followed by evaporating to dryness is effected to obtain the monoor diammonic phosphate, or
• ammonium phosphate obtained by such a process is'completely soluble, but the total amount of phosphoric anhydride P 0 in the insoluble phosphates is lost in the final fertilizer.
• a watersoluble nitrophosphate fertilizer can be produced by ammoniating wet process polyphosphoric acid.
• the condensed phosphorous molecule being a sequestering agent for metal ions.
• the fertilizer so obtained contains useful elements contributed by the wet process phosphoric acid.
• the starting polyphosphoric acid is costly.
• the process of the invention avoids the drawbacks of the prior methods and enables a totally soluble ammonium phosphate for agricultural use to be obtained from wet process phosphoric acid, without having to remove insoluble phosphates as in the first two processes mentioned, and without using polyphosphoric acid as in the third process hereinbefore described.
• the process of the invention is based on obtaining an exact proportion of polyphosphate during manufacture which maintains the metal impurities in solution, said process being applied to a silica-free phosphoric acid.
• the object of the invention is a process for obtaining a totally water-soluble nitrogen-phosphate fertilizer, consisting essentially in using a phosphoric acid produced by the wet process; in removing the fluosilicic acid existing in the said polyphosphoric acid by a known treatment by the use of a sodium salt, followed by separating out the insolubilized sodium fluosilicate; in ammoniating the defluosilicated acid to a pH of 5 to 6, and preferably from 5.5 to 6.0; in removing substantially all water from the reaction mixture, and in dry treating with urea the ammoniated phosphate so obtained, in amounts of 0.2 to 0.9 molecule of urea per mole of P 0 for 15 to 70 minutes at between and C., after which the mixture is allowed to cool and, if necessary, diluted with water.
• French Patent No. 1,411,254 describes fireproof paint compositions comprising a waterinsoluble ammonium polyphosphate, which is the reaction product of a monoammonium phosphate or phosphoric acid and urea.
• the reaction with urea is carried out at high temperatures between about and 260 C. and the reaction lasts for one to two hours.
• the mole ratio of nitrogen to phosphorus is between about 0.7 and 5.
• the reaction conditions provided for in French Patent No. 1,411,254 are imposed by the use of ammonium polyphosphates as fireproof additives.
• French Patent No. 1,437,486 describes a process for the manufacture of chain condensed ammonium phosphates in which urea is used for treating phosphates at reaction temperatures in the range of 180-400 C., while 0.5 to 2.5 atom-gram of nitrogen are used per molecule of water relased by the formation of the polyphosphate. These reaction conditions enable a special class of polyphosphates to be obtained.
• the invention also turns the reaction of urea and orthophosphates to account, but uses it for manufacturing fertilizers from wet process phosphoric acid containing various impurities such as iron, aluminium, calcium and magnesium phosphates among others.
• impurities such as iron, aluminium, calcium and magnesium phosphates among others.
• urea is used to cause the aforesaid impurities to be solubilized, as well as those which may be contained in the other constituents of liquid fertilizers.
• a monoammonium phosphate containing a small amount of diammonium phosphate and having a pH (1% solution of P in the range of between 5.0 and 6.0 and preferably between 5.5 and 6.0 rather than a monoammonium phosphate.
• reaction (1) is only possible when starting with the orthophosphate group with formation of polyphosphate by condensation of the phosphoric acid molecule, according to Equation 2 for instance:
• reaction (1) remains bound to the phosphoric or polyphosphoric acid groups, thus enabling an ammonium-enriched phosphate product to be obtained as compared with the starting monoammonium phosphate.
• the process of the invention makes use of a phosphoric acid obtained by the wet process and containing 30 to 55% by weight of P 0 and preferably 30 to 40%.
• the silica is removed from the wet process phosphoric acid by insolubilizing the fluosilicic acid found in the phosphoric acid.
• This treatment is carried out with an equimolecular amount of fluosilicic acid to a sodium salt, preferably sodium carbonate, sulphate or sulphide.
• the insoluble fluosilicate is removed from the solution by filtration or decantation. It should, however, be noted that when a 54-55% commercial phosphoric acid is used this preliminary treatment is not necessary.
• the defluosilicated phosphoric acid is then subjected to a known ammoniating process until the pH of the reaction mixture is between 5 and 6 and preferably between 5.5 to 6.0.
• the prepared paste can be dried to obtain a substantially anhydrous phosphate suitable for the next step in the process of the invention.
• This step which is the essential characteristic of the invention, consists in the addition of urea to said dry phosphate.
• the proportions of the reagents, expressed in the mole ratio of urea to P 0 available in the phosphate are in the range of 0.2 to 0.9.
• the mixture of said phosphate is heated at between 130 and 170 C. for 15 to 70 minutes to permit conversion of the starting orthophosphate. A dry mixture is thus obtained which is allowed to cool and which constitutes a completely water-soluble nitrogen-phosphate fertilizer.
• a wet process phosphoric acid titrating 30% of P 0 was used, obtained by sulfuric attack on a natural phosphate from TOGO.
• the phosphoric acid was first defluosilicated by the addition of sodium carbonate in an amount of 15.9 g./kg. of acid.
• the solution thus obtained was filtered and neutralized by ammonia to pH 5.8 in Examples 1 to 5, to pH 4.7 for Example 6, to pH 6 for Example 7 (1% P 0 solutions).
• a phosphate was produced which was dried and mixed with variable amounts of urea and then dried at a temperature of from C. before the condensation reaction.
• the following specific examples illustrate the reaction conditions of treatment of said phosphate by urea.
• EXAMPLE 1 70 g. of urea is added to an intimately mixed with 350 g. of phosphate. This mixture is heated at 135 C. for 30 minutes. The product so obtained is completely soluble and the solution remains clear for several weeks. Its analytic composition is as follows:
• EXAMPLE 2 This process is the same as that used in Example 1 except that the proportions of reagents are 350 g. phosphate for 30 g. urea. After the addition of Water the resulting product gives a clear solution which remains stable for several weeks and has the following proportions on analysis:
• the product obtained after reaction with urea has the following composition:

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Fertilizers (AREA)

Applications Claiming Priority (1)

Publications (1)

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Family Applications (1)

Country Status (6)

Cited By (4)

Families Citing this family (2)

Family Cites Families (5)

• 1967
  • 1967-05-22 FR FR107296A patent/FR1533272A/fr not_active Expired
• 1968
  • 1968-05-15 US US729367A patent/US3586495A/en not_active Expired - Lifetime
  • 1968-05-21 NL NL6807191A patent/NL6807191A/xx unknown
  • 1968-05-21 DE DE19681767547 patent/DE1767547B1/de active Pending
  • 1968-05-22 GB GB24398/68A patent/GB1182395A/en not_active Expired
  • 1968-05-22 BE BE715547D patent/BE715547A/xx unknown

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